Seal ring

ABSTRACT

Provided is a seal ring configured so that stable lubrication performance can be provided across a wide range of rotation speed. A seal ring for sealing a clearance between a rotary shaft and a housing includes inclined grooves formed at a sliding surface so as to be arranged in a circumferential direction, the inclined grooves being open on an outer diameter side of the seal ring to generate a drawing pressure. The seal ring further includes supply grooves being open on a sealed fluid side of the seal ring and extending in a radially outward direction toward inner diameter sides of the inclined grooves.

TECHNICAL FIELD

The present invention relates to a seal ring used for sealing aclearance between a rotary shaft and a housing, and specifically relatesto a seal ring used in a state in which the seal ring is attached to anannular groove, i.e., a so-called stuffing box.

BACKGROUND ART

Typically, a seal ring is attached to the outer periphery of a rotaryshaft. A sliding surface of the seal ring slides in close contact with asliding surface formed at the rotary shaft, and accordingly, the sealring seals a clearance between the rotary shaft and a housing to preventleakage of sealed fluid (e.g., liquid).

For maintaining sealing properties in the seal ring for a long period oftime, conflicting conditions of “sealing” and “lubrication” need to besatisfied. Particularly in recent years, while prevention of leakage ofthe sealed fluid has been made for, e.g., environmental measures, ademand for friction reduction has increased for reducing a mechanicalloss. Friction reduction can be accomplished by the technique ofgenerating a dynamic pressure between the sliding surfaces by rotationof the rotary shaft to slide the sliding surfaces with a fluid film ofthe sealed fluid being interposed.

For example, a seal ring as described in Patent Citation 1 has beenknown as the seal ring configured to generate the dynamic pressurebetween the sliding surfaces by rotation of the rotary shaft. The sealring of Patent Citation 1 is attached to an annular groove provided atthe outer periphery of a rotary shaft. The seal ring is pressed to ahousing side and one side wall surface side of the annular groove by thepressure of high-pressure sealed fluid, and a sliding surface at oneside surface of the seal ring slides in close contact with a slidingsurface at one side wall surface of the annular groove. Moreover, at thesliding surface at one side surface of the seal ring, multiple dynamicpressure grooves opening on an inner diameter side are provided in acircumferential direction. The dynamic pressure groove includes a deepgroove at the center in the circumferential direction and shallowgrooves formed continuously to both sides of the deep groove in thecircumferential direction, extending in the circumferential direction,and having bottom surfaces inclined such that the shallow groovesgradually become shallower toward terminal ends. When the rotary shaftand the seal ring rotate relative to each other, the sealed fluid isintroduced from the inner diameter side of the sliding surface into thedeep grooves. Moreover, a negative pressure is generated in each shallowgroove of the seal ring on a side opposite to a rotation direction ofthe rotary shaft. Meanwhile, the sealed fluid introduced into the deepgrooves is supplied to each shallow groove on the same side as therotation direction, and therefore, a positive pressure is generated insuch a shallow groove. Then, the positive pressure increases due towedge action caused by the inclined bottom surface of therotation-direction-side shallow groove, and is generated across theentirety of the dynamic pressure groove. Accordingly, the force ofslightly separating the sliding surfaces from each other, i.e.,so-called buoyancy, is obtained. The sliding surfaces are slightlyseparated from each other, and therefore, the high-pressure sealed fluidflows into a portion between the sliding surfaces from the innerdiameter side of the sliding surface and the sealed fluid flows out ofthe rotation-direction-side shallow grooves generating the positivepressure to the portion between the sliding surfaces. Thus, a fluid filmis formed between the sliding surfaces, and lubricity between thesliding surfaces is maintained.

CITATION LIST Patent Literature

Patent Citation 1: JP 9-210211 A (third page, FIG. 3)

SUMMARY OF INVENTION Technical Problem

In the seal ring of Patent Citation 1, the sliding surface of the rotaryshaft moves relative to the dynamic pressure grooves in thecircumferential direction. The positive pressure increases as the numberof rotations of the rotary shaft increases, and the fluid film is formedbetween the sliding surfaces to enhance the lubricity of the slidingsurface. However, the dynamic pressure groove is configured such thatboth shallow grooves are positioned on the same circumference withrespect to the deep groove. Thus, particularly upon high-speed rotation,cavitation is caused in a region where a great positive pressure and agreat negative pressure are generated in the circumferential direction.Due to greater variation in the buoyancy generated across thecircumferential direction of the sliding surface, there is a probabilitythat an adverse effect on the fluid film, such as a non-uniform fluidfilm, is caused and the lubricity becomes unstable.

The present invention has been made in view of such a problem, and anobject of the present invention is to provide a seal ring configured sothat stable lubrication performance can be provided across a wide rangeof rotation speed.

Solution to Problem

For solving the above-described problem, a seal ring according to thepresent invention is seal ring for sealing a clearance between a rotaryshaft and a housing, including: inclined grooves formed at a slidingsurface so as to be arranged in a circumferential direction, theinclined grooves being open on an outer diameter side of the seal ringto generate a drawing pressure; and supply grooves being open on asealed fluid side of the seal ring and extending in a radially outwarddirection toward inner diameter sides of the inclined grooves. Accordingto the aforesaid feature, high-pressure sealed fluid introduced throughinner-diameter-side openings of the supply grooves is, on the outerdiameter side, drawn by the drawing pressure due to a flow in the outerdiameter direction in each inclined groove upon rotation of the rotaryshaft, and the flow of sealed fluid in the radially outward direction isformed among the supply grooves and the inclined grooves. Thus, a fluidfilm can be formed with favorable balance in the circumferentialdirection among the supply grooves and the inclined grooves, andtherefore, stable lubrication performance can be provided across a widerange of rotation speed.

It may be preferable that a seal portion is formed continuously in thecircumferential direction and positioned between the supply grooves andthe inclined grooves. According to this preferable configuration, thesupply grooves and the inclined grooves between which the flow of sealedfluid in a radial direction is formed are separated from each other inthe radial direction by the seal portion, and therefore, the fluid filmis formed with favorable balance in the circumferential direction on theseal portion.

It may be preferable that the supply grooves are equally arranged in thecircumferential direction. According to this preferable configuration,the flow of sealed fluid in the radial direction is formed withfavorable balance in the circumferential direction on the seal portion.

It may be preferable that the supply grooves are communicated with eachother through a communication groove which is positioned on the innerdiameter side of the seal portion and extends in the circumferentialdirection. According to this preferable configuration, the high-pressuresealed fluid introduced through the inner-diameter-side openings of thesupply grooves is supplied in the circumferential direction by thecommunication groove, and therefore, the flow of sealed fluid in theradial direction is reliably formed with favorable balance in thecircumferential direction on the seal portion.

It may be preferable that the seal ring further comprise dynamicpressure grooves each formed at the sliding surface between adjacent twoof the supply grooves in the circumferential direction and being open onthe sealed fluid side of the seal ring. According to this preferableconfiguration, a negative pressure generated by the inclined grooves canbe partially cancelled by a positive pressure generated in the dynamicpressure grooves, and therefore, the flow of sealed fluid in the radialdirection is easily formed on the seal portion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating a seal ring according to afirst embodiment of the present invention by partially-simplifiedillustration.

FIG. 2 is a sectional view illustrating a sealing structure for aclearance between a rotary shaft and a housing by the seal ringaccording to the first embodiment.

FIG. 3 is a partial side view of the seal ring according to the firstembodiment.

FIGS. 4A and 4B are partial side views and A-A sectional views of theseal ring according to the first embodiment for schematicallyillustrating a fluid film formation process in accordance with stages.

FIG. 5 is a partial side view and an A-A sectional view of the seal ringaccording to the first embodiment for schematically illustrating,following FIGS. 4A and 4B, the fluid film formation process inaccordance with stages.

FIG. 6 is a partial side view of a seal ring according to a secondembodiment of the present invention.

FIG. 7 is a B-B sectional view of the seal ring of FIG. 6 .

FIG. 8 is a partial side view of a seal ring according to a thirdembodiment of the present invention.

FIG. 9 is a partial side view of a seal ring according to a fourthembodiment of the present invention.

FIG. 10 is a partial side view of a seal ring according to a fifthembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, modes for carrying out a seal ring according to the presentinvention will be described based on embodiments.

First Embodiment

A seal ring according to a first embodiment will be described withreference to FIGS. 1 to 5 . Hereinafter, the right side in the plane ofpaper of FIG. 2 will be described as a sealed fluid side L, and the leftside in the plane of paper will be described as an atmosphere side A.Note that the fluid pressure of sealed fluid on the sealed fluid side Lwill be described as a higher pressure than an atmospheric pressure.Moreover, a sliding surface includes a flat surface and a grooverecessed as compared to the flat surface. For the sake of convenience indescription, the flat surface forming the sliding surface is, in theside views, indicated by the color of white, and the groove forming thesliding surface is indicated by dots.

The seal ring 1 according to the present embodiment seals a portionbetween a rotary shaft 2 and a housing 3 of a rotary machine, the rotaryshaft 2 and the housing 3 rotating relative to each other. In thismanner, the seal ring 1 partitions the inside of the housing 3 into thesealed fluid side L and the atmosphere side A (see FIG. 2 ), andprevents leakage of the sealed fluid from the sealed fluid side L to theatmosphere side A. Note that the rotary shaft 2 and the housing 3 aremade of a metal material such as stainless steel. Moreover, the sealedfluid is one used for the purpose of cooling and lubricating, e.g., anot-shown gear and a not-shown bearing provided in a machine chamber ofthe rotary machine, such as oil.

As illustrated in FIGS. 1 to 3 , the seal ring 1 is a component moldedwith resin such as PTFE, and is provided with a joint portion 1 a at onespot in a circumferential direction to form a C-shape. The seal ring 1is used with the seal ring 1 being attached to an annular groove 20, theannular groove 20 being provided along the outer periphery of the rotaryshaft 2 and having a rectangular sectional shape. The rotary shaft 2rotates clockwise as indicated by a white arrow in FIG. 3 , and the sealring 1 rotates counterclockwise relative to the annular groove 20 of therotary shaft 2. Note that in FIG. 2 , the section of the seal ring 1along a radial direction is schematically illustrated.

Moreover, the seal ring 1 has a rectangular sectional shape. The sealring 1 is pressed to the atmosphere side A by the fluid pressure of thesealed fluid acting on a side surface on the sealed fluid side L, andaccordingly, a sliding surface S1 formed on a side surface 10(hereinafter sometimes merely referred to as a “side surface 10”) sideon the atmosphere side A slidably closely contacts a sliding surface S2on a side wall surface 21 (hereinafter sometimes merely referred to as a“side wall surface 21”) side of the annular groove 20 on the atmosphereside A. Further, in response to stress in an expansion direction due tothe fluid pressure of the sealed fluid acting on an innercircumferential surface, the seal ring 1 is pressed in a radiallyoutward direction, and accordingly, an outer circumferential surface 11closely contacts an inner circumferential surface 31 of a shaft hole 30of the housing 3.

Note that the sliding surfaces S1, S2 form a substantial sliding regionbetween the side surface 10 of the seal ring 1 and the side wall surface21 of the annular groove 20 of the rotary shaft 2. Moreover, anon-sliding surface S1′ is formed continuously to an outer diameter sideof the sliding surface S1 on the side surface 10 side, and a non-slidingsurface S2′ is formed continuously to an inner diameter side of thesliding surface S2 on the side wall surface 21 side (see FIG. 2 ).

As illustrated in FIGS. 1 to 4 , the sliding surface S1 formed on theside surface 10 side of the seal ring 1 includes a flat surface 16,multiple supply grooves 13 extending in the radial direction from aninner-diameter-side end portion of the side surface 10, a communicationgroove 14 communicated with outer-diameter-side end portions of thesupply grooves 13 and formed continuously in a substantially annularshape across the joint portion 1 a, and multiple inclined grooves 15formed inclined to the direction of rotation of the rotary shaft 2 fromthe vicinity of an outer-diameter-side end portion of the communicationgroove 14 (i.e., an outer-diameter-side end portion of a later-describedseal portion 16 a) and communicated with an outer-diameter-side endportion of the side surface 10 (on the atmosphere side A). Note that thesupply grooves 13 are arranged at equal intervals in the circumferentialdirection of the sliding surface S1, except for the vicinity of thejoint portion 1 a. Moreover, the inclined grooves 15 extend from thesliding surface S1 to the non-sliding surface S1′, and are arranged atequal intervals in the circumferential direction, except for thevicinity of the joint portion 1 a.

The flat surface 16 includes the seal portion 16 a positioned betweenthe outer-diameter-side end portion of the communication groove 14 andan inner-diameter-side end portion of each of the multiple inclinedgrooves 15 and formed continuously in a substantially annular shapeacross the joint portion 1 a, an inner-diameter-side lubrication portion16 b sandwiched by adjacent ones of the supply grooves 13 in thecircumferential direction, and an outer-diameter-side lubricationportion 16 c sandwiched by adjacent ones of the inclined grooves 15 inthe circumferential direction (see FIG. 3 ). The dimension of the sealportion 16 a in the radial direction is 1/20 (preferably ⅕ to 1/50) ofthe dimension of the sliding surface S1 in the radial direction, and isthe substantially same dimension as the dimension of theouter-diameter-side lubrication portion 16 c in the circumferentialdirection. Note that the dimension of the seal portion 16 a in theradial direction is preferably short, considering that the sealed fluideasily moves over the seal portion 16 a.

As illustrated in FIGS. 2 to 5 , the supply groove 13 supplies,regardless of rotation/stop of the rotary shaft 2, the sealed fluid to aportion between the sliding surfaces S1, S2 when the sealed fluid has ahigher pressure than that of atmospheric air. The supply groove 13 has arectangular shape as viewed from the side. The supply groove 13 opens onthe inner diameter side (i.e., the sealed fluid side) of the slidingsurface S1, and is communicated with the communication groove 14 on theouter diameter side. Moreover, a bottom surface 13 d (see FIG. 4A) ofthe supply groove 13 is formed flat, and is parallel with the flatsurface 16. The depth of the supply groove 13 is several tens to severalhundreds of μm and preferably 100 to 200 μm. Note that the depth of thesupply groove 13 may be much deeper (e.g., up to about a depth of 1 mm).

The communication groove 14 is formed to extend in the circumferentialdirection at a position on the outer diameter side with respect to thecenter of the sliding surface S1 in the radial direction, has an arcshape as viewed from the side, and has a shorter dimension in the radialdirection than the dimension of the supply groove 13 in thecircumferential direction. Moreover, a bottom surface 14 d of thecommunication groove 14 is formed flat, is parallel with the flatsurface 16, and is formed continuously to the bottom surface 13 d of thesupply groove 13. The depth of the communication groove 14 issubstantially the same as that of the supply groove 13 (see FIG. 4A).

As illustrated in FIGS. 2 to 5 , the inclined groove 15 extends to theouter diameter side in the rotation direction of the rotary shaft 2 fromthe seal portion 16 a, i.e., extends inclined with respect to the radialdirection, and has the function of generating a drawing pressure in theinclined grooves 15 due to a flow in the radially outward direction uponrotation of the rotary shaft 2. The inclined groove 15 is configuredsuch that a closed portion 15 d extending along the outer-diameter-sideend portion of the seal portion 16 a, a planar outer inclined wallportion 15 b positioned on an opposite rotation side of the rotary shaft2 and formed perpendicularly to a bottom surface 15 e, a planar innerinclined wall portion 15 c positioned on a rotation side of the rotaryshaft 2 and formed perpendicularly to the bottom surface 15 e, and anopening 15 a crossing the outer inclined wall portion 15 b and the innerinclined wall portion 15 c and communicated with a non-sliding surfaceS1′ side (i.e., the atmosphere side A) form a parallelogram shape asviewed from the side. The inclined groove 15 has the substantially samedimension in the circumferential direction as the dimension of thecommunication groove 14 in the radial direction, and has a longerdimension in an extension direction than the dimension in thecircumferential direction. Moreover, the bottom surface 15 e of theinclined groove 15 is formed flat, and is parallel with the flat surface16. The depth of the inclined groove 15 is shallower than those of thesupply groove 13 and the communication groove 14.

Further, the outer-diameter-side lubrication portion 16 c having ashorter dimension in the circumferential direction than the dimension ofthe inclined groove 15 in the circumferential direction is interposedbetween adjacent ones of the inclined grooves 15 in the circumferentialdirection. Note that the dimensions of these portions may be the same aseach other, or the outer-diameter-side lubrication portion 16 c may havea longer dimension. Moreover, the multiple inclined grooves 15 may beformed with a curvature such that the outer-diameter-side lubricationportions 16 c are formed to the outer diameter side with thesubstantially equal width.

Next, fluid film formation between the sliding surface S1 of the sealring 1 and the sliding surface S2 of the side wall surface 21 of theannular groove 20 (hereinafter sometimes merely referred to as “betweenthe sliding surfaces S1, S2”) will be described with reference to FIGS.4A, 4B, and 5 . Note that a case where the rotary shaft 2 rotatesclockwise as indicated by the white arrow in FIG. 3 , i.e., a case wherethe seal ring 1 rotates counterclockwise relative to the annular groove20 of the rotary shaft 2 in FIG. 3 , will be described herein by way ofexample. Further, note that each of FIGS. 4A, 4B, and 5 schematicallyillustrates an association between an enlarged partial side view of theseal ring 1 as viewed from the side and an A-A sectional view cut alongthe supply groove 13, the communication groove 14, and the inclinedgroove 15 of the enlarged partial side view.

First, as illustrated in FIG. 4A, when the rotary shaft 2 stands still,the supply grooves 13 and the communication groove 14 are filled withthe sealed fluid due to the fluid pressure. Moreover, the high-pressuresealed fluid is supplied to the supply grooves 13 and the communicationgroove 14, and due to a resting pressure, the force of separating thesliding surfaces S1, S2 acts on the supply grooves 13 and thecommunication groove 14.

Next, as illustrated in FIG. 4B, upon rotation of the rotary shaft 2,the sliding surface S1 on the side surface 10 side slides on the slidingsurface S2 on the side wall surface 21 (see FIG. 2 ) side. Accordingly,the sealed fluid in the communication groove 14 generates a clockwiseflow along the communication groove 14. Moreover, although not shown inthe figure, the sliding surface S2 passes over the supply grooves 13,and therefore, the sealed fluid flows out of the supply grooves 13 tofollow the rotation direction of the rotary shaft 2.

Meanwhile, on the outer diameter side with respect to the seal portion16 a, the sealed fluid and air in the inclined grooves 15 move from aclosed portion 15 d side to an opening 15 a side of the inclined groove15, and accordingly, the drawing pressure is generated from the closedportion 15 d side to the opening 15 a side of the inclined groove 15.Thus, a negative pressure is generated on the closed portion 15 d side.

The sealed fluid forming a fluid film on the seal portion 16 a is drawninto the inclined grooves 15 by such a negative pressure. Accordingly,the sealed fluid in the communication groove 14 leaks out to a sealportion 16 a side, and the flow F of moving the sealed fluid over theseal portion 16 a from the communication groove 14 and drawing thesealed fluid into the inclined grooves 15 is formed (see FIG. 5 ). Thefluid film is reliably formed on the seal portion 16 a, and lubricity isenhanced. The fluid film of the sealed fluid is formed between thesliding surfaces S1, S2 due to, e.g., the flow F and the restingpressure, and the lubricity is enhanced.

Moreover, the multiple inclined grooves 15 are formed at equal intervalsacross the circumferential direction, and therefore, a dynamic pressureis substantially uniformly generated across the outer diameter side ofthe sliding surface S1 (i.e., the seal portion 16 a). Thus, stablebuoyancy can be obtained across the circumferential direction.

Further, as described above, not only the sealed fluid is mainlysupplied from the communication groove 14 to a portion between thesliding surface S2 and the seal portion 16 a, but also the high-pressuresealed fluid is supplied from the inclined grooves 15 and thecommunication groove 14 to the outer-diameter-side lubrication portion16 c interposed between adjacent ones of the inclined grooves 15 in thecircumferential direction and is supplied from the inner diameter sideof the sliding surface S1 and the supply grooves 13 to theinner-diameter-side lubrication portion 16 b defined by adjacent ones ofthe supply grooves 13 and the communication groove 14. Thus, the fluidfilm of the sealed fluid having a substantially equal thickness isformed between the sliding surfaces S1, S2.

As described above, the high-pressure sealed fluid introduced throughinner-diameter-side openings of the supply grooves 13 moves over theseal portion 16 a, and on the outer diameter side, is drawn by thedrawing pressure due to the flow in the radially outward direction inthe inclined grooves 15 upon rotation of the rotary shaft 2.Accordingly, the flow F of sealed fluid in the radially outwarddirection is formed among the supply grooves 13, the communicationgroove 14, and the inclined grooves 15. Thus, the fluid film can beformed with favorable balance in the circumferential direction among thesupply grooves 13, the communication groove 14, and the inclined grooves15, and therefore, stable lubrication performance can be provided acrossa wide range of rotation speed.

Moreover, the sealed fluid is sufficiently supplied as described above,and therefore, the fluid film can be reliably formed between the slidingsurfaces S1, S2 across a wide range of rotation speed. Thus, thelubricity of the seal ring 1 can be enhanced.

Further, the supply grooves 13, the communication groove 14, and theinclined grooves 15 among which the flow of sealed fluid in the radialdirection is formed are separated in the radial direction by the sealportion 16 a, and therefore, the fluid film is formed with favorablebalance in the circumferential direction on the seal portion 16 a. Withthis configuration, the lubricity of the seal portion 16 a can beenhanced.

In addition, the multiple supply grooves 13 are equally arranged in thecircumferential direction, and therefore, the flow of sealed fluid inthe radial direction is formed with favorable balance in thecircumferential direction on the seal portion 16 a.

Moreover, the multiple supply grooves 13 are, on the inner diameter sideof the seal portion 16 a, communicated with each other through thecommunication groove 14 extending in the circumferential direction, andtherefore, the high-pressure sealed fluid introduced through theinner-diameter-side openings of the supply grooves 13 is supplied in thecircumferential direction by the communication groove 14. Thus, the flowof sealed fluid in the radial direction is reliably formed withfavorable balance in the circumferential direction on the seal portion16 a.

Further, the seal ring 1 is in the C-shape, and therefore, sealperformance can be stably maintained even when the circumferentiallength of the seal ring 1 changes due to thermal expansion/contraction.

Second Embodiment

Next, a seal ring according to a second embodiment will be describedwith reference to FIGS. 6 and 7 . Note that the same reference numeralsare used to represent the same components as those described in theabove-described embodiment, and overlapping description thereof will beomitted.

The seal ring 101 in the second embodiment will be described. Asillustrated in FIG. 6 , in the present embodiment, a sliding surface S1(see FIG. 2 ) formed at a side surface 110 of the seal ring 101 includesa flat surface 16, multiple supply grooves 13, a communication groove14, multiple inclined grooves 15, and a dynamic pressure groove 12provided between adjacent ones of the supply grooves 13 in acircumferential direction.

The dynamic pressure groove 12 has the function of generating a dynamicpressure according to rotation of a rotary shaft 2. The dynamic pressuregroove 12 includes a deep groove 120 opening on an inner diameter side(i.e., the sealed fluid side) of the seal ring 101 and provided at thecenter in the circumferential direction and a pair of shallow grooves121, 122 (i.e., positive pressure generators and negative pressuregenerators) formed continuously from both sides of the deep groove 120in the circumferential direction and extending in the circumferentialdirection. An inner-diameter-side lubrication portion 16 b in aninverted U-shape as viewed from the side is arranged between the dynamicpressure groove 12 and each of the supply grooves 13 adjacent to such adynamic pressure groove 12 in the circumferential direction and thecommunication groove 14. Note that in FIGS. 6 and 7 , the right sidewith respect to the deep groove 120 in the plane of paper is the shallowgroove 121 (i.e., the positive pressure generator), and the left side inthe plane of paper is the shallow groove 122 (i.e., the negativepressure generator).

Specifically, as illustrated in FIG. 7 , the deep groove 120 has abottom surface formed flat, and the shallow grooves 121, 122 have bottomsurfaces as inclined surfaces formed such that the shallow grooves 121,122 gradually become shallower from a deep groove 120 side to terminalends in the circumferential direction. Moreover, the bottom surface ofthe deep groove 120 is formed much deeper than deepest portions of theshallow grooves 121, 122, and the depth of the deep groove 120 isseveral tens to several hundreds of μm and preferably 100 to 200 μm.

According to such a configuration, in fluid film formation between thesliding surfaces S1, S2, a negative pressure is generated in eachshallow groove 122 (hereinafter merely referred to as a “shallow groove122”) of the seal ring 101 on a side (i.e., the left side in the planeof paper of FIG. 6 ) opposite to a rotation direction of the rotaryshaft 2. Meanwhile, sealed fluid introduced into the deep grooves 120 issupplied to each shallow groove 121 (hereinafter merely referred to as a“shallow groove 121”) of the seal ring 101 on the same side (i.e., theright side in the plane of paper of FIG. 6 ) as the rotation direction,and a positive pressure is generated in such a shallow groove 121 due towedge action caused by the inclined surface. Then, the positive pressureis generated across the entirety of the dynamic pressure grooves 12, andaccordingly, the force of slightly separating the sliding surfaces S1,S2 from each other, i.e., so-called buoyancy, is obtained. That is, thepositive pressure (i.e., the buoyancy) can be generated not only on anouter diameter side of the sliding surfaces S1, S2 but also on an innerdiameter side by the dynamic pressure grooves 12. Thus, responsivenessof fluid film formation to rotation of the rotary shaft 2 can beenhanced.

Moreover, the force of sucking the sealed fluid present between thesliding surfaces S1, S2 around the shallow groove 122 generating thenegative pressure acts on such a shallow groove 122. Thus, the sealedfluid is supplied to the shallow groove 122 and a surroundinginner-diameter-side lubrication portion 16 b thereof from the supplygroove 13 adjacent to such a shallow groove 122 in the circumferentialdirection. Further, the shallow groove 122 as the negative pressuregenerator in the dynamic pressure groove 12 opens on the inner diameterside (i.e., the sealed fluid side), and the sealed fluid is alsointroduced from the inner diameter side of the sliding surface S1. Thus,the sealed fluid is easily held on the shallow groove 122.

Further, the negative pressure generated by the inclined grooves 15 canbe partially cancelled by the positive pressure generated on the outerdiameter side of the sliding surface S1, and the sliding surfaces S1, S2can be easily separated from each other by the dynamic pressuregenerated across the entirety of the dynamic pressure grooves 12. Thus,the flow of sealed fluid in a radial direction is easily formed on aseal portion 16 a.

In addition, the dynamic pressure groove 12 arranged on the innerdiameter side of the sliding surface S1 may be freely formed, and may beformed as, e.g., a T-shaped groove, a Rayleigh step, or a spiral groove.

Third Embodiment

Next, a seal ring according to a third embodiment will be described withreference to FIG. 8 . Note that the same reference numerals are used torepresent the same components as those described in the above-describedembodiments, and overlapping description thereof will be omitted.

The seal ring 201 in the third embodiment will be described. Asillustrated in FIG. 8 , in the present embodiment, a sliding surface S1(see FIG. 2 ) formed at a side surface 210 of the seal ring 201 includesa flat surface 16, multiple supply grooves 13, a communication groove14, multiple inclined grooves 15, and a dynamic pressure groove 112provided between adjacent ones of the supply grooves 13 in acircumferential direction.

The dynamic pressure groove 112 includes a deep groove 220 opening on aninner diameter side (i.e., the sealed fluid side) of the seal ring 201,provided at the center in the circumferential direction, andcommunicated with the communication groove at an outer-diameter-side endportion and a pair of shallow grooves 121, 122 formed continuously fromboth sides of the deep groove 220 in the circumferential direction andextending in the circumferential direction. An inner-diameter-sidelubrication portion 16 b in an L-shape as viewed from the side isarranged between the dynamic pressure groove 112 and each of the supplygrooves 13 adjacent to such a dynamic pressure groove 112 and thecommunication groove 14.

According to such a configuration, in fluid film formation between thesliding surfaces S1, S2, sealed fluid can be supplied to thecommunication groove 14 not only from the supply grooves 13 but alsofrom the deep grooves 220 of the dynamic pressure grooves 112. Thus, afluid film can be more reliably formed between the sliding surfaces S1,S2 across a wide range of rotation speed, and lubricity of the seal ring201 can be enhanced.

Fourth Embodiment

Next, a seal ring according to a fourth embodiment will be describedwith reference to FIG. 9 . Note that the same reference numerals areused to represent the same components as those described in theabove-described embodiments, and overlapping description thereof will beomitted.

The seal ring 301 in the fourth embodiment will be described. Asillustrated in FIG. 9 , in the present embodiment, a sliding surface S1(see FIG. 2 ) formed at a side surface 310 of the seal ring 301 includesa flat surface 16, multiple supply grooves 113, and a single inclinedgroove 115 inclined to a rotation direction of a rotary shaft 2 from thevicinity of an outer-diameter-side end portion of each supply groove 113(e.g., an outer-diameter-side end portion of a seal portion 16 a) to anouter-diameter-side end portion of the side surface 310. According tosuch a configuration, a flow F (see FIG. 5 ) moving over the sealportion 16 a at outermost diameter portions of the sliding surfaces S1,S2 can be formed with a simple configuration.

Fifth Embodiment

Next, a seal ring according to a fifth embodiment will be described withreference to FIG. 10 . Note that the same reference numerals are used torepresent the same components as those described in the above-describedembodiments, and overlapping description thereof will be omitted.

The seal ring 401 in the fifth embodiment will be described. Asillustrated in FIG. 10 , in the present embodiment, a sliding surface S1(see FIG. 2 ) formed at a side surface 410 of the seal ring 401 includesa flat surface 16, multiple supply grooves 213, multiple communicationpaths 214 each communicated with adjacent two of the supply grooves 213,and multiple inclined grooves 215 inclined to a relative turningdirection from the vicinity of an outer-diameter-side end portion ofeach communication path 214 (e.g., an outer-diameter-side end portion ofthe seal portion 16 a) to an outer-diameter-side end portion of the sidesurface 410. According to such a configuration, a flow F (see FIG. 5 )moving over the seal portion 16 a at outermost diameter portions of thesliding surfaces S1, S2 can be formed with a simpler configuration thanthose of the first to third embodiments.

The embodiments of the present invention have been described above withreference to the drawings, but specific configurations are not limitedto these embodiments. The present invention also includes even changesand additions made without departing from the scope of the presentinvention.

For example, the configuration of the dynamic pressure groove of thesecond embodiment or the third embodiment may be applied to the fourthand fifth embodiments.

Moreover, the form in which the rotary shaft 2 is turned clockwise togenerate the dynamic pressure in the inclined grooves 15 has beendescribed. However, the rotary shaft 2 is rotated counterclockwise tomove the sealed fluid from the opening 15 a side to the closed portion15 d side of the inclined groove 15, and therefore, outflow of thesealed fluid can be reduced with favorable responsiveness.

Further, the number and shape of dynamic pressure grooves, supplygrooves, communication paths, or inclined grooves provided at thesliding surface S1 or the non-sliding surface S1′ of the seal ring maybe changed as necessary such that a desired dynamic pressure effect isobtained. Note that the location and shape of the deep groove of thedynamic pressure groove to which the sealed fluid is introduced, thelocation and shape of the supply groove to which the sealed fluid isintroduced, the location and shape of the communication path to whichthe sealed fluid is introduced, and the location and shape of theinclined groove to which the sealed fluid is introduced may be changedas necessary according to the assumed degree of abrasion of the slidingsurface.

In addition, the inclined groove may have a bottom surface as aninclined surface formed such that the inclined groove gradually becomesshallower from the opening side to the closed portion. With such a form,the drawing pressure is more easily generated due to taper action.

Moreover, the seal ring may be formed in an annular shape without thejoint portion 1 a, and the outer shape thereof is not limited to acircular shape as viewed from the side. The seal ring may be formed in apolygonal shape.

Further, the seal ring is not limited to the rectangular sectionalshape, and for example, may have a trapezoidal sectional shape or apolygonal sectional shape. The seal ring may be configured such that theside surface forming the sliding surface S1 is inclined.

In addition, the grooves described in the above-described embodimentsmay be formed at the sliding surface S2 of the annular groove 20 of therotary shaft 2.

Moreover, the oil has been described as the example of the sealed fluid,but the sealed fluid may be liquid such as water or coolant or gas suchas air or nitrogen.

REFERENCE SIGNS LIST

1 to 401 Seal ring

2 Rotary shaft

3 Housing

10 Side surface

12 Dynamic pressure groove

13 Supply groove

14 Communication groove

15 Inclined groove

16 Flat surface

16 a Seal portion

16 b Inner-diameter-side lubrication portion

16 c Outer-diameter-side lubrication portion

20 Annular groove

21 Side wall surface

110 Side surface

112 Dynamic pressure groove

113 Supply groove

214 Communication path

115 Inclined groove

210 Side surface

213 Supply groove

215 Inclined groove

310 Side surface

410 Side surface

S1, S2 Sliding surface

S1′, S2′ Non-sliding surface

The invention claimed is:
 1. A seal ring housed in an annular groovewhich has a rectangular sectional shape and is formed in an outerperiphery of a rotary shaft inserted into a shaft hole of a housing, forsealing a clearance between the rotary shaft and the housing, wherein: aside surface of the seal ring includes a sliding surface which isslidably brought into close contact with a side wall surface of theannular groove, an outer peripheral surface of the seal ring is broughtinto close contact with an inner peripheral surface of the shaft hole,and the seal ring comprises inclined grooves formed so as to communicatewith an outer-diameter-side end portion of the side surface of the sealring; and supply grooves being open on a sealed fluid side of the sealring and extending in a radially outward direction toward inner diametersides of the inclined grooves.
 2. The seal ring according to claim 1,wherein a seal portion is formed continuously in a circumferentialdirection and positioned between the supply grooves and the inclinedgrooves.
 3. The seal ring according to claim 1, wherein the supplygrooves are equally arranged in a circumferential direction.
 4. The sealring according to claim 1, wherein the supply grooves are communicatedwith each other through a communication groove which is positioned onthe inner diameter side of the seal portion and extends in acircumferential direction.
 5. The seal ring according to claim 1,further comprising dynamic pressure grooves each formed at the slidingsurface between adjacent two of the supply grooves in a circumferentialdirection and being open on the sealed fluid side of the seal ring. 6.The seal ring according to claim 2, wherein the supply grooves areequally arranged in a circumferential direction.
 7. The seal ringaccording to claim 2, wherein the supply grooves are communicated witheach other through a communication groove which is positioned on theinner diameter side of the seal portion and extends in a circumferentialdirection.
 8. The seal ring according to claim 2, further comprisingdynamic pressure grooves each formed at the sliding surface betweenadjacent two of the supply grooves in a circumferential direction andbeing open on the sealed fluid side of the seal ring.
 9. The seal ringaccording to claim 3, wherein the supply grooves are communicated witheach other through a communication groove which is positioned on theinner diameter side of the seal portion and extends in a circumferentialdirection.
 10. The seal ring according to claim 3, further comprisingdynamic pressure grooves each formed at the sliding surface betweenadjacent two of the supply grooves in a circumferential direction andbeing open on the sealed fluid side of the seal ring.
 11. The seal ringaccording to claim 4, further comprising dynamic pressure grooves eachformed at the sliding surface between adjacent two of the supply groovesin a circumferential direction and being open on the sealed fluid sideof the seal ring.